Children Putting to a Test

¶ … Children

PUTTING to a TEST

How Effective is the Influenza Vaccine among Children?

The purpose of this paper is to discover and discuss the effectiveness of the Influenza vaccine in children. Children and the elderly are the two age groups, which experience most of the complications of an influenza infection, which can reach epidemic proportions. Efforts to contain the spread are mainly on widespread vaccination, undertaken by the Centers for Disease Control and Prevention.. Internationally recognized bodies recommend immunization of healthy children as a public health measure (Jefferson, 2009).

Success of Vaccination

Vaccination is a generally highly effective preventive strategy, some of which have become real successes (Watson, 2001). Vaccines have been in use for smallpox, diphtheria, poliomyelitis, measles, mumps and rubella. Others are under improvement for influenza, hepatitis a and B, meningococcal disease, pneumococcal infection, and varicella. Under development are vaccines against cytomegalovirus infection, group B. streptococcal disease, HIV, hepatitis C, rotavirus infection, pertussis in adolescents and adults, human papillomavirus, genital herpes, tuberculosis, malaria, meningococcal disease serotype B, organisms and infection with multidrug-resistant staphylococci. A decade ago, a live cold-adapted, nasally administered influenza vaccine, was tested with 10,000 subjects, including 6,500 children aged 1-18. They showed no serious adverse reactions. Previous flu vaccines similar to FluMist were also well tolerated by more than 800 tested children and adults. FluMis was projected to be approved by the end of 2001 (Watson).

Concerns of that time included administering of routine vaccine on healthy young children and research on live attenuated, killed virus vaccines, recombinant hemagglutin subunit vaccines and new adjuvants for old vaccines (Watson).

Nasal Spray Vaccines for Children

Jefferson and his research team (2009) appraised 16 randomized control trials and 18 case cohort studies and conducted almost 300,000 observations on the effects of influenza vaccine on healthy young children. The researchers also assessed the efficacy of the flu vaccine as a preventive of confirmed flu and of flu-like illness and documented its adverse effects. Live vaccines showed 82% efficacy and 33% effectiveness in older children. Inactivated vaccines had 59% efficacy and live vaccines, 36%. The authors found that nasal spray vaccines from weakened influenza viruses could prevent illness better at 82% than injected vaccines from killed virus at 59%. Neither of the two types was found effective in preventing flu-like illnesses. Evidence of efficacy was inadequate for children under 2. And the safety of the vaccines could not be analyzed because of the lack of standardized information. There was very little information on the safety of inactivated vaccines, which were the most commonly used in young children (Jefferson et al.).

Efficacious in Healthy Children

Manzoli and his research team (2007) took over where Jefferson and his team left off. Manzoli and his team conducted another meta-analysis, using meta-regression techniques and a larger sampling. Their randomized clinical studies assessed the efficacy of influenza vaccine in healthy children and adolescents below 18 years in preventing naturally occurring influenza. More than 70% of the respondents were in good health.

Results of the studies revealed vaccination efficacy at 36% against clinically diagnosed illnesses and 67% against laboratory-confirmed cases (Manzoli et al.).

The results provided evidence on the relevant benefit of influenza vaccination for the prevention of clinically and laboratory-confirmed influenza cases in health children 2 years old and older (Manzoli et al., 2007). Data provided were insufficient to include younger children. Although no safety and cost considerations were addressed concerning efficacy, the overall findings suggested vaccination as a possible option for the prevention of influenza in healthy children 2 years and older (Manzoli).

The Limits of the 2009 Influenza a Vaccine

The Influenza a or H1N1 pandemic of 2009 revealed children's lack of measurable immunity to the virus (Fiore and Neuzil, 2009). They also developed severe Influenza a-related symptoms. The Centers for Disease Control and Prevention confirmed 224 laboratory-confirmed deaths among children as of December 5, 2009. The spread of the virus was estimated to be greater than estimated. Children were, therefore, among the target recipients for the limited amount of available vaccines in most areas. Recommended immunization was 2 doses for seasonal influenza vaccine and for children below 9 years of age and receiving vaccination for the first time. The current recommendation for the 2009 Influenza a mono-valent vaccines is 2 doses in children 10 years and younger. An earlier report on the efficacy of a single 15-ug dose of an un-adjuvanted inactivated influenza a vaccine can elicit significant increases in antibodies in more than 90% of healthy infants and young children. A succeeding single dose 21 days later raised antibody levels even more. The report also said that the un-adjuvanated vaccine was tolerated and safe. A single dose may be immunogenic in most young children, but 1 dose may not provide adequate protection for all young children (Fiore & Neuzil).

Using the immunogenicity data of the report, this study concluded that only 1 dose of the 2009 influenza a vaccine provides protection to many un-vaccinated children in some seasons (Fiore & Neuzil, 2009). Earlier studies, however, consistently demonstrated greater vaccine effectiveness in 2 doses than 1 dose. The vaccine may not protect all children with a single dose. Epidemiological circumstances in every country and vaccine formulations are factors. Measurable immunity in all age groups must be achieved before 2 doses can be recommended for infants and young children (Fiore & Neuzil).

Effectiveness v 2003-2005 Season Cases

Eisenberg and his team (2005) conducted a case-control study with 485 children aged 6-59 months during the 2003-2004 and 2004-2005 influenza seasons. The children received care in an inpatient, emergency department and outpatient clinics for acute respiratory infections. Of their total, 6% among the 2003-2004 case subjects and 19% of the 2004-2005 case subjects were full vaccinated. Full vaccination among the 2003-2004 cases led to significantly fewer influenza-related inpatient emergency department or outpatient clinic visits at 57%. Vaccine effectiveness among the 2003-2004 cases was lower at 44%. Partial vaccination was not effective in either season (Eisenberg et al.).

American children aged 6 to 59 months have been observed to undergo hospitalizations, emergency department and outpatient visits for influenza every year (Eisenberg et al., 2005). This research team's case-control study suggested that more than half of the visits could have been prevented if the recommended influenza vaccination was administered to children. Partial vaccination was not effective. The study finding supported previous recommendations for vaccinating children against influenza. It also pointed to the importance of receiving the recommended number of vaccinations (Eisenberg et al.).

2 Doses for Optimal Protection

The largest evaluation study of Influenza vaccine among children 6-23 months old was recently conducted by Ritzwoller and her team (2005). It was also a comparative effectiveness between 1 and 2 doses among children 6 months to 8 years old who received medical attention for Influenza-like illnesses. The team used records from outpatient and emergency department visits and immunization for a retrospective cohort study. International Classification of Diseases, ninth revision, codes was used to define Influenza-like illnesses and pneumonia and Influenza outcomes. A total of 29,726 children participated. Before the study, 17.3% were 6-23 months old. At the peak of the activity, 7.5% and 9.9% of those 6 months to 8 years old were fully or partially vaccinated against Influenza, respectively. Vaccine efficiency against Influenza-like illness and pneumonia and Influenza was 25% and 49%, respectively for those fully vaccinated children 6-23 months old. There was no significant reduction of Influenza-like illnesses or pneumonia and Influenza rates among partially vaccinated children 6-23 months old. Vaccine efficiency against Influenza-like illnesses and pneumonia and Influenza for fully vaccinated children 6 months to 8 years old was 23% and 51%, respectively. Vaccine efficiency was significant for pneumonia and Influenza at 23% for those only partially vaccinated (Ritzwoller et al.).

The team study (2005) concluded that Influenza vaccination provided substantial protection for those full vaccinated despite a sub-optimal match between the vaccine and the predominantly circulating strains at the time. It also assumed that vaccination could provide some protection to partially vaccinated children less than 9 years. The study findings suggested the need to vaccinate previously unvaccinated children 6 months to 8 years old with 2 doses for optimal protection. It furthermore found Influenza vaccination effective in preventing Influenza-like illnesses among children 6-23 months and those 6 months to 8 years old (Ritzwoller et al.).

2 Doses for 6-59 Months Old Children

Another team (Shueler et al., 2007) addressed the need to measure Influenza vaccine effectiveness among young children when antigenic match between vaccine and circulating viruses was sub-optimal. This team conducted a study with children aged 6-59 months who were medical attended for laboratory-confirmed Influenza during the 2003-2004 flu season. These children were 290 Influenza case patients under medical care from November 1, 2003 to January 32, 2004. Vaccine effectiveness among these patients who were fully vaccinated was 49%. Vaccination was not effective on partially vaccinated children 6-23 months old but was 65% among those 24-59 months as against unvaccinated (Shueler et al.).

This separate study (2007) concluded that full vaccination provides significant and measurable protection against laboratory-confirmed Influenza among children aged 6-59 months during a season of sub-optimal vaccine match. Partial vaccination was not effective on children 6-23 months. This meant that full vaccination is necessary to optimally protect children of this age group from Influenza (Shueler et al.).

The results are consistent with those of other evaluative studies on children through randomized, controlled trials for efficacy and observational studies for effectiveness (Shueler et al., 2007). Vaccine effectiveness depends on the characteristics of the study population, specificity of the outcome, and the Influenza season. It was dissimilar to the findings of Ritzwoller and his team in that Shueler and team's subjects had more exposure to Influenza. The more specific outcome of laboratory-confirmed Influenza made the detection possible. And Shueler and his team's findings were similar to Ritzwoller and his team's in that the findings of both teams offered assurance that vaccination of young children would be beneficial, even in a year with sub-optimal match (Shueler et al.).

Vaccination Efficacy not Found

A case -- cohort study aimed at measuring vaccination among children aged 6-59 months during 2 Influenza seasons (Szilagyi et al., 2008). Participating patients were 165 and 80 inpatient/emergency department and 74 and 95 outpatient Influenza cases. Another group of 4,500 inpatient/ED and more than 600 outpatient sub-cohorts, respectively, were also evaluated. The team compared vaccination status of laboratory-confirmed Influenza cases with random sales in 3 counties during the 2 seasons. Results showed that vaccine effectiveness could not be determined for any season, age or setting after adjusting for county, sex, insurance, chronic conditions and timing of vaccination. The case-cohort research design might be inefficient and insufficiently account for important factors, like the inclination to obtain care. The team concluded that further studies should be conducted using other designs to evaluate the yearly impact of Influenza vaccination programs for children (Szilagyi et al.).

Live Attenuated Influenza Vaccine or LAIV

This is the approved vaccine in the United States for persons aged 2-49 (Ambrose et al., 2008). It is administered as an intranasal spray. It has provided high levels of efficacy in both match and mismatched strains in this age group. Comparative studies between LAIV and inactivated Influenza vaccine in children showed that patients with LAIV had up to 53% fewer cases of illness than with the other vaccine. The most common adverse reactions are runny nose or nasal congestion in the said age group and less than 100 degrees Fahrenheit fever in children. Formulations of LAIV are under experiment (Ambrose et al.).

Live attenuated Influenza viruses replicate primarily in the nose and throat area to induce the body's immune response (Ambrose et al., 2008). These viruses do not replicate too well in lower airways and lung where the temperature is warmer. During replication, viral proteins will be perceived by the immune system, which responds to natural infection by Influenza viruses. The vaccine is now currently approved for children 2 years old and older. Tests showed up to 93.4% efficacy against illness after the first year of vaccination. It reached 100% after the second year. LAIV also protects against antigenically mismatched strains as a single dose in children 1.5 to 18 years of age. As to dose, tests showed that a single dose had a 58% efficacy while two doses had 89%. Thus, the recommended dose is 2. The vaccine was also evaluated as safe in more than 18,000 tested children less than 5 years old except for nasal congestion or runny nose (Ambrose et al.).

There is concern about these viruses re-assorting with circulating seasonal Influenza viruses and evolve into easily transmissible types (Ambrose et al., 2008). Authorities addressed this concern by conducting clinical trials during months when the viruses are not likely to circulate. This can be done in an isolation facility between April and December. When a pandemic is imminent, the risks should be weighed against the benefits before the massive use of the vaccine. This will be the decision of public health authorities (Ambrose et al.).